1. Technical Field
The present invention relates to a technology for performing positioning of a moving body using wireless communication.
2. Related Art
The global positioning system (GAPS) is well known as a wide-area positional information service provided to moving bodies such as vehicles. However, GAPS has a problem in that service is unavailable in the shadows of buildings and indoors. In addition, GAPS is dependent on infrastructure, that is, GAPS satellites. The positional information service becomes unavailable in the event of an infrastructure failure or disruption of service.
Another wireless positioning technology has been proposed (refer to, for example, US Patent Application Publication No. 2013/0310067). In this technology, a reference station is provided near a road (a predetermined path). A receiver is mounted in a moving body. The receiver receives transmission waves from the reference station. When the moving body moves along the predetermined path, a positioning trajectory is generated. The positioning trajectory indicates the changes in reception strength (received signal strength indicator (RSSI)) detected by the receiver. The positioning trajectory and a reference trajectory that is prepared in advance (a reference value for reception strength at each point on the predetermined path) are compared. The position of the moving body is estimated from the location at which the positioning trajectory and the reference trajectory most coincide.
A plurality of locations having a high degree of coincidence between the positioning trajectory and the reference trajectory may be present. Alternatively, there may be no location that can be said to have an obviously higher degree of coincidence compared to other locations. In such instances, the location having the highest value of the degree of coincidence may not necessarily indicate the correct position. Therefore, in such instances, when the positioning result is determined from the location at which the degree of coincidence is the highest, as in the conventional technology, a problem occurs in that whether or not the positioning result is reliable cannot be determined.